hello-c-gnome3: Document build dependencies.

* HACKING: Mention Gtk3 dependency.

diff --git a/HACKING b/HACKING
index b02003b772a7f079d11929f5c9d19a1acff569d9..4c602997ab2b559dac51761be797de4cb81c6010 100644 (file)
--- a/HACKING
+++ b/HACKING
@@ -320,6 +320,13 @@ are skipped. To this effect, you need to install also:
 If you want to exercise the sample programs in gettext-tools/examples/, you
 also need to install:
 
+  * The Gtk3 GUI toolkit library
+    + Homepage: https://www.gtk.org/
+    + Pre-built package name:
+      - On Debian and Debian-based systems: libgtk-3-dev,
+      - On Red Hat distributions: gtk3-devel.
+      - Other: https://repology.org/project/gtk/versions
+
   * The Qt GUI toolkit library
     + Homepage: https://www.qt.io/
     + Pre-built package name: